[SOLVED] cli for changing rights to existing shared folder

I have six shared folders, each in a separate account.
I need to change the rights to these shared folders from viewer (r) to manage (rwid) for 40 accounts.
I found how to create and assign rights at the command line but not how to use zmmailbox modifyFolderGrant to change the rights to existing shared folders (not the entire account but a folder inside the account).
Thanks for any help.
Anne